Measurement of the ratio of branching fractions B(B-0 -> K*(0)gamma)/B(B-s(0) -> phi gamma)

The ratio of branching fractions of the radiative B decays B-0 -> K*(0)gamma and B(0)s -> phi gamma has been measured using 0.37 fb(-1) of pp collisions at a center of mass energy of root s = 7 TeV, collected by the LHCb experiment. The value obtained is B(B-0 -> K*(0)gamma)/B(B(0)s ->phi gamma) = 1.12 +/- 0.08(-0.04-0.08)(+0.06+0 .09), where the first uncertainty is statistical, the second systematic, and the third is associated with the ratio of fragmentation fractions f(s)/f(d). Using the world average for B(B-0 -> K*(0)gamma) = (4.33 +/- 0.15) x 10(-5), the branching fraction B(B(0)s -> phi gamma) is measured to be (3.9 +/- 0.5) x 10(-5), which is the most precise measurement to date.